One approach to identifying valve temperature may be to sense temperature via an electric valve actuator, where the actuator coil resistance is correlated to temperature. In one approach, when the valve is in an un-actuated state, a current is passed through the coil that is too small to cause the valve to move, but large enough to provide a corresponding voltage indicative of the coil resistance. Likewise, the current applied to hold a valve open/closed may also be correlated to resistance. The identified resistance can then be correlated to temperature.
However, the inventors herein have recognized a potential disadvantage with such an approach. Specifically, such temperature sensing is typically needed at a significantly slower sampling rate than intake/exhaust valve cycling driven by engine firing and the firing order. In other words, taking a reading at every un-actuated valve position may be too cumbersome and increase chronometric loading, while at the same time increasing noise since actual temperature variation bandwidths are typically much lower than engine firing frequencies. Further, the appropriate time to sense temperature for each actuator may depend on the location of the valve coupled to the actuator, the type of valve coupled to the actuator, and/or whether the actuator opens, or closes, a valve. Further, from which actuator the temperature sensing is needed may vary with engine operation and the end use of the temperature information.
In one approach, the above issues may be addressed by a method of operation for an engine including an electrically actuated engine valve, with at least an actuator, the method comprising: applying a potential to generate a current in the actuator indicative of temperature at least partially during a substantially non-moving condition of the actuator; and adjusting a timing of the application of the potential based on valve location in the cylinder head or actuator type. The application of the potential may thus correspond to a resistance measurement. Further, the valve location may include a whether a valve is located in different cylinders, or located on the intake side versus the exhaust side. As another example, actuator type may include whether the valve actuator is an opening or closing actuator for the valve.
In this way, a temperature reading from among a plurality of actuator types and/or valve locations can be coordinated with engine firing and engine crankshaft rotation so that temperature sampling may be achieved among a plurality of actuators. Furthermore, the temperature reading may be achieved by adjusting the timing of the resistance measurement based on changes in engine firing order (e.g., due to cylinder deactivation), or changes in active valve operation and engine stroke (e.g., changing timing of a valve from operating during and intake stroke to during an exhaust stroke, or changing a number of strokes in a cycle, such as 6-stroke cycles).